Effect of Hole Density and Confining Pressure on Mechanical Behavior of Porous Specimens:An Insight from Discrete Element Modeling

Hole-like defects are very common in natural rock or coal mass,and play an important role in the failure and mechanical behaviors of rock or coal mass.In this research,multi-holed coal specimens are constructed numerically and calibrated based on UDEC-GBM models.Then,the strength,deformation and failure behavior of the porous specimens are analyzed,with consideration of hole density(P)and confining pressure(σ_(3)).The simulation results are highly consistent with those available experiment results,and show that the compressive strength decreases exponentially with the increasing hole density.The strength loss is mainly caused by the reduction of cohesion when P<P_(cr)(critical hole density)and the reduction of frictional angle when P>P_(cr).Also,the increasing hole density linearly reduces the tangent and secant modulus and causes greater nonlinear deformation of multi-holed specimens.Finally,the failure patterns,coalescence mechanism and damage behavior of the multi-holed specimens are revealed based on the analysis of mesoscopic displacement fields and stress distribution around holes.This research promotes a better understanding of the effects of hole density and confining pressure on the failure and mechanical behavior of porous geomaterials.